Archaea Flashcards
what are the two major phyla of archaea?
- euryarchaeota
2. crenarcheaota (part of the TACK superphyla)
what are archaea also known as?
extremophiles
- most species of archaea are adapted to extreme conditions
what makes up the archaeal ultrastructure?
- s-layer
- cell wall: pseudomurein
- cell envelope structures
- cytoplasmic membrane
what is the structure/role of the archaeal s-layer?
- outermost structure
- major component of the cell envelope
- involved in cell shape
- often glycosylated
- not in all archaea
what is the structure/role of the pseudomurein cell wall?
- heteropolymer of disaccharide peptides, linked by beta 1,3 bonds
- not always present: most archaea have no pesudomurein
- similar to bacterial peptidoglycan
- resistant to lysozymes and most cell wall inhibitor antibiotics (penicillin)
what are some unusual cell envelope structures in archaea?
- archaellum:
- equivalent of the flagellum as it enables some archaea to move
- has different assembly: powered by ATP, not H+ - cannulae
- extensions from the cell - hooks
- help cells adhere and form microcolonies
what is the structure/role of the archaeal cytoplasmic membrane?
- phospholipids contain no fatty acids, but isoprenes instead
- phospholipids are ether-linked
- more stable than bacterial membranes
- present as monolayers or bilayers
what is the organisation of chromosomes and DNA replication in archaea?
- circular chromosome and plasmids
- contains histones
- multiple replication origins, sharing many eukaryotic properties
- encode polymerase B (eukarya) and D (specific to archaea)
what is involved in transcription and RNA processing in archaea?
- a single RNAP exists, similar to eukaryotic RNA pol II
- presence of introns (like eukarya)
- presence of machinery to remove introns in tRNA and rRNA
- genes are organised in operons (like bacteria)
what is involved in translation in archaea?
- coupled with transcription (like bacteria)
- involves translation factors (like eukarya)
- ribosomes are 70S
how is the physiology of archaea diverse?
wide range of habitats:
- hydrothermal vents (hot springs)
- light source for energy: phototrophs
- use chemical compounds: chemotrophs - Antarctica: effluents from geothermal stations
- use reducing sources: organic and inorganic - volcanic environments
- use carbon sources: organic
what are hyperthermophiles?
- both euryarchaeota and crenarchaeota
- growth temp 80-120C
- require sulphur for growth
- usually acidophiles (pH 1-3)
what is are 2 model examples of a hyperthermophile?
- Acidianus infernus (crenarchaeota)
- isolated in geothermic hot spring
- optimal growth 75C, pH 2.5-3
- grows anaerobically (produces H2S) or aerobically (produces H2SO4) - Thermococcus barosii
- isolated from hydrothermal vent
- optimal growth 82C, pH 2.5-3
- grows anaerobically and require sulphur
how do sulphate-reducing archaea cause problems in oil refinery?
- they produce hydrogen sulphide which is highly soluble in oil
- this increases sulphur emissions when the oil is burned
- increased cost in oil refining
- sulphide attacks metal pipelines, causing leaks and corrosion
what are halophiles?
- mostly euryarchaeota
- found in evaporating ponds, Dead Sea and Great Salt Lake
- need up to 5M NaCl for growth (0.6M in seawater)
